1. Field of the Invention
The present invention relates to a bicycle wheel rim, more particularly to a bicycle wheel rim formed with a wear-indicating projection to inform the user of the condition of the bicycle wheel rim that is in frequent frictional contact with a brake pad.
2. Description of the Related Art
A bicycle wheel rim generally includes an annular rim body with spaced left and right tire retaining walls, and a spoke-mounting wall interconnecting the tire retaining walls. A tire is to be installed between the tire retaining walls. Each of the tire retaining walls has a brake pad contacting surface opposite to the other one of the tire retaining walls for contacting a brake pad. After a period of use, the brake pads and the tire retaining walls of the bicycle wheel rim will tend to wear out. Although wearing of the tire retaining walls occurs at a rate much slower than that of the brake pads, wearing of the tire retaining walls should not be neglected since it affects the strength of the bicycle wheel rim. It is desirable that wearing of the tire retaining walls of the bicycle wheel rim be indicated to remind the user when replacement of the bicycle wheel rim has to be conducted.
FIG. 1 illustrates a known bicycle wheel rim 1 which is formed with a wear-indicating groove 13 in the brake pad contacting surface 121 of each of its tire retaining walls 12. During use of the bicycle wheel rim 1, the brake pad contacting surfaces 121 are frequently in frictional contact with brake pads (not shown) of a bicycle and are thus gradually worn out to eventually render the grooves 13 to be non-observable. At this time, the user can be notified that wearing of the bicycle wheel rim 1 to a predetermined extent has occurred, and that the bicycle wheel rim 1 has to be replaced with a new one to ensure safety of the user.
However, it is found that during use of the bicycle wheel rim 1, the tire retaining walls 12 are applied with a stress, which concentrates on portions that are formed with the wear-indicating grooves 13 to result in deformation or even breakage of the tire retaining walls 12. This condition is aggravated when the bicycle wheel rim has wider tire retaining walls, i.e., the width of the tire retaining walls measured between their radial inner edges and their radial outer edges, is relatively wide.
Therefore, the main object of the present invention is to provide a bicycle wheel rim formed with a wear-indicating projection for informing the user of the condition of the bicycle wheel rim, without the danger of undesired weakening of the bicycle wheel rim.
Accordingly, the bicycle wheel rim of this invention includes an annular rim body having a central axis. The annular rim body includes spaced left and right annular side walls adapted for retaining a bicycle tire therebetween. Each of the side walls has a radial inner edge proximate to the central axis, a radial outer edge distal to the central axis, and a lateral outer brake pad contacting surface opposite to the other one of the side walls. The annular rim body further includes an annular base wall interconnecting the radial inner edges of the left and right sidewalls. The brake pad contacting surface of each of the left and right side walls is formed with a wear-indicating projection adapted to be in frictional contact with a brakepad. The wear-indicating projection is formed as a continuous annular projection that extends along a respective one of the side walls. The brake pad contacting surface gradually wears out during use of the bicycle wheel rim to eventually render the wear-indicating projection to wear off, thereby indicating that wearing of the bicycle wheel rim to a predetermined extent has occurred.